In recent years there has been an increased need for break-in resistant exterior door locking systems, particularly in urban areas where crime rates have increased dramatically.
A typical security door lock system includes at least one deadbolt which is extendable from a door through an aperture in a hollow metal door frame by inserting and rotating a matched key. One of the most common ways for a thief to break into such a lock, is by inserting a prying tool between the door and the frame for the purpose of dislodging the bolt from the frame cavity. In an attempt to prevent this type of break-in, many door manufacturers or builders today provide an exterior door with a "latch guard" attached to the door and extending over a portion of the frame when the door is closed. The primary purpose of the latch guard is to block the opening between the door and the frame in the vicinity of the lock. While the latch guard has been partially successful for the purpose of preventing or deterring break-ins, it also is susceptible to being pried open.
This problem was addressed by Mascotte in U.S. Pat. No. 5,131,189 which discloses an "antiprying member" consisting of a metal plate attached to the external surface of the frame surrounding the latch guard. There are, however, several notable problems with the Mascotte antiprying member.
First, Mascotte's antiprying plate protrudes beyond the surfaces of the door and frame, and therefore detracts from the aesthetic appearance of the entire door lock and frame system.
Second, since the antiprying member sits on top of the external frame surface, it accommodates a door having a latch guard which also protrudes out from the external door surface, further detracting from the aesthetic quality of the entire system.
Third, one of the reasons that a typical latch guard is susceptible to prying is that the door frame wall below the latch guard is collapsible. Mascotte's antiprying member does not add any extra strength to the frame wall disposed behind the latch guard.
Accordingly, it is an object of the present invention to provide a door lock system in which a latch guarded lock is provided in a door frame system in which all of the external surfaces of the door, frame and latch guard are flush.
Another object is to provide a door lock and frame system in which the region of the door frame which is covered by the latch guard, is reinforced to prevent collapse.
Another object of the invention is to provide a door lock system in which the box surrounding the lock ("lock box") is reinforced to prevent collapse.